Magnetic core switching circuit



Jan. 19, 1960 A. H. BOBECK MAGNETIC CORE SWITCHING CIRCUIT Filed Oct 16, 1956 INFORMATION I /NPUT OUTPUT CIRCUITS 2 f L Ad I 2 A J ll 2 5 2 v 2 :1 I. r m T 9 2 2 1 3 I H T M m 2 z I- H nu 2 w 9 L w 4 A a 2 v H H H w w, n V\)/ )/A|\3 I a 2 z! 2 z, 2 H .O\ u 2 2 3 2 X1. a 3L 7 a INVENTOR By AH. BOBECK A TTORN Q United States Patent MAGNETIC CORE SWITCHING CIRCUIT Andrew H. Bobeck, Chatham, N.J., assignor t0 Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Application October 16, 1956, Serial No. 616,164

13 Claims. (Cl. 340-174) This invention relates to magnetic core circuits and particularly to such circuits comprising switches presettable in accordance with a predetermined code.

The property of certain ferrites of remaining in a particular condition of magnetic saturation to which driven by an applied magnetomotive force is well known. This property, manifested in the core by a substantially rectangular hysteresis characteristic, presents in such cores a convenient means for accomplishing essential switching functions in gating and logic operations of data processing systems. When a core is set, that is, is in one particular condition of remanent saturation, a current pulse, producing a magnetomotive force in a direction opposite to the set condition, applied to an activating winding inductively coupled to the core, will cause the core to switch to the opposite, or reset, condition of remanent saturation. This switching or change of direction of flux in the core, will induce a voltage in an output winding also inductively coupled to the core. If, however, the core under discussion is already in the reset magnetic condition, virtually no flux change will result as the current pulse is applied to the activating winding and no effective voltage will be induced in the output winding of the core. Under these circumstances it isobvious that the presence of a signal on output terminals "connected to the output winding of the core at the application of an advance pulse will be determined by the particular condition of magnetic saturation to which the core has previously been driven.

In addition to the aforementioned principles of core switching another expedient of considerable importance in realizing the 'most advantageous use of magnetic cores is described by M. Karnaugh in his' Patent No. 2,719,961 of October 4, 1955. In the circuits there described the output winding of a magnetic core is connected at its input to the output side of an activating winding. When .an advance current pulse is applied to the activating winding and the core is caused to switch thereby, an electromotive force is induced across the output winding in the direction such as to cause the advance current to flow through that output winding. .As applied in the arrangement of Karnaugh cited, the principle makes possible a selection switch comprising magnetic cores serially connected by activating windings. The advance current will then cause any set cores to be reset; the resetting causing the advance current to flow to desired loads through the output windings of the cores so reset. This principle of steering the advance current as determined by particular cores' set is also applied generally in my copending application Serial No. 616,308, filed October 16, 1956. In that application coupling loops connecting pairs of cores of a shift register are connected 'so that the output winding of a core is similarly connected to the activating winding of that core. The advance current is then caused to pass either through the loop and operate to switch the succeeding core or it fiscaused to by-pass the output winding andswitchiiiiwiiidin'g 'of' the succeeding core, depending upon 2,922,145 Patented Jan. 19, 1960 ice whether or not the activated core is in a set condition.

The principles described above have been utilized according to this invention to provide a magnetic selection switch capable of selecting particular cores of a magnetic core memory matrix and supplying switching current to the cores selected. In connection with providing switching currents for word-organized coincident current matrices generally, simultaneous currents must be applied to the cores of the columns of the matrix in which the information bits of a word appear at the same time that a switching current is applied to cores of the row containing the word. Heretofore it has been found necessary to provide a driving current source for each of the columns of the matrix. According to the principles of this invention a considerable saving in the number of such driving current sources is realized. In theory, only one current source would be necessary to drive the cores of any number of columns reasonably contemplated in a magnetic core matrix by employing the switch of this invention.

Accordingly, it is an object of this invention to provide an improved means for supplying driving currents to a large number of magnetic core loads.

It is another object of this invention to provide an improved magnetic core means for selectively applying activating currents to predetermined ones of a plurality of loads and by-passing the remainder of the loads.

Another object of this invention is to selectively apply switching currents to groups of magnetic cores of a magnetic core matrix from a minimal number of current sources.

The foregoing and other objects of this invention are realized in one illustrative embodiment thereof comprising a series of magnetic cores capable of being switched from one condition of magnetic saturation to another by I an applied magnetomotive force of suitable polarity. Ac-

cording to one feature of this invention each of the cores has an activating and an output winding thereon, the windings being serially connected. Load means, such as, for example, the switching leads of a magnetic core storage matrix, are connected between the terminals of the output windings of each core and each activating winding is also connected to the junction of the activating and output windings of a preceding core. Particular cores of the series are set in accordance with the particular loads to which current is to be applied. When an activating current is applied to the serially connected activating windings the particular cores set will be reset and, in accordance with the principle described hereinbefore, the activating current will fiow in the output windings of the particular cores and to the loads connected thereto in series. Suitable unidirectional current elements are utilized in connection with each output winding to isolate the unwanted current path during the load selecting operation.

Thus, according to one aspect of this invention, each of the preset cores presents a closed current path to the selected load and each core not so preset presents an open current path to its associated load, a closed circuit path shunting the load being presented in the latter case.

A complete understanding of the objects and features of this invention together with its organization and structure can be gained from a consideration of the detailed description thereof which fOllOWs when taken in conjunction with the accompanying drawing, the single figure of which is a schematic representation of a magnetic core selecting switch according to this invention, depicted as applied to a well-known magnetic core information storage matrix and associated circuits.

Referring now specifically to the drawing, the selecting switch 10 embodying the principles of this invention I 1s seen to comprise a plurality of magnetic cores 20 having a substantiallyrectangular -asa, b, 0, n, the cores of the switch associated therewith are the cores 20 20 20 and 20 respectively. Each of the coresZtl has inductively coupled thereto an input. winding 21, an activating winding 22, and an output winding 23. The output windings 23 of each of the cores 2% are connected through diodes 24and 25 to opposite ends of a write conductor 26 threading the cores 31 of each of the columns of the matrix 30. One side of each of the output windings 23 is also connected to-one side of an activating winding22. Connecting theone side of each of the activating windings 22 also to the other side of the activating winding'22 of a'succeeding core through the diode 24- is an advance conductor 27. In accordance with the manner in which theactivating windings 22 and the output windings23 are connected, two possible circuit paths arev available at each section of the switch 10 represented by a core 20. One circuit includes'the activating winding 22, the output winding 23, the diode write conductor '26, and advance conductor 27. The other possible circuit by-passes the' output winding 23 and write conductor26, and passes directly from the activating winding 22 through thediode 24 to the advance conductor 27.

The magnetic core storage matrix may be comprised of the cores 31 arranged in rows and columns such as the columns a, b, c, n, and the rows 1, 2, 3, m. In addition to the switching conductors 26 threading the cores 31 of the columns a through it, eachof the columns of cores has threaded therethrough'a' detecting conductor 29 connected from information input-output circuits 40 to a ground conductor 28. Each of the rows of cores 1 through In has threaded therethrough a pair of conductors: a read conductor 32 and awrite conductor 33,v both of which conductors are connected between an access switch 50 and the ground conductor '28. The input windings 21 of each of the cores 20 are connected on one side to the input-output circuits 40 and on the other a side to a ground conductor 34.

The information input-output c1rcuits .40 and the access switch 59 may advantageously comprise the corresponding circuitsused in connection with the'magnetic core memory circuit which I have described in detail with J. H. Felker in our copending application Serial No. 555,889, filed December 28, 1955. .Thus the access switch 50) of the type described by M. Karnaugh in the aforementioned patent and comprises a plurality of magnetic cores, alternate ones of which are driven by alternate phase switching pulses supplied by a pulse source 60 via the ga and (p conductors 35 and 36. Each pulse operates in its phase in a manner such as to switch one core, thereby selecting a current path to a selected load and setting the next succeeding core of the next phase of operation. The switching pulses are in this manner alternately and sequentially applied to the conductors32 and.

33 of the rows of the matrix. coincidentally with the (p phase of operation of the switch 50 under the control'of a pulse supplied by the source 60, a current pulse is supplied via the 2 conductor 37 to the activating windings 22 of the selecting switch 10. The pulse source 60 is advantageously of the magnetic core flip-flop type described in the above-mentioned application Serial. No. 555,889 and in my application Serial No. 555,976, filed December 28, 1955.

In the first phase of operation of the access switch 50 a full-amplitude current pulse is appliedto a read conductor 32'threading the cores of a row of the matrix. Assume, for purposes of description, this row to be the row 2 having contained therein the binary information word 01.1 0. Thestorage inthe cores of that row of a binary 1 is, for convenience, indicatedinthe drawingby shading the cores. Upon the application of the 0 phase full-amplitude current pulse to the cores 31 of row'2, the cores 31 of columns b and c of'row 2 will be switched to their reset magnetic condition. The other cores of that row will not be switched and a voltage signal will be induced in the detecting conductors 29 of columns b and 0 only. The word thus'read out of the matrix during the e or read phase is temporarily stored in the information input-output circuits 40. In connection with the latter circuits, means may be provided to make this information available to external utili- Zation devices, not shown, if and when desired. If the irn- V ten in the matrix to replace the word read out imme diately preceding, appropriate cores 20 of the switch 10 may be set by the circuits 4t) underthe control of external switching means also notshown. Assuming the former case, that the word read out is to be restored to the same row of the matrix, a 1 or write phase halfamplitude current pulse is applied by the access switch 50 to the write conductor 33. At the same time a halfamplitude current pulse is applied via the pa conductor 37 from the pulse source 60 to the activating windings 21 of the cores 20. This current pulse, termed halfamplitude in view of the fact that it is of substantially half the magnitude necessary to switch the magnetic con dition of a core 31 of the matrix 30, is nevertheless effectively full-amplitude with respect to the cores 20 of the switch 10. The comparative magnetomotive forces developed by the o2 current pulses supplied by the source 60 are readily adjusted by a suitable selection of turns ratios of the conductors 26 and the windings 22. Since the cores 20 and 20 were the only cores selectively set. by the circuits-40 only these cores will be'reset and, in accordance with the principles hereinbefore described, the gag half-amplitude current pulse will be caused to flow in. the output windings 23 of only those cores. i Accordingly, the a high-amplitude current pulse wi follow the circuit which may be traced'from the source- 60 as follows: conductor 37, activating winding 22 of the core 20.,, diode 24, advance 27,, activating and output windings 22 and 23 of the core 20 diode 25, write conductor 26 of column [2, advance conductor 27 activating and output windings 22 and 23 of the core 20 diode 25,

write conductor 26 of column c, advance conductor 27 I et cetera, and finally the activating winding 22, diode 24,v and advance conductor 27 to ground. .Thus for particular columns of the matrix, the activating current pulse will by-pass the output winding 23 and the write conductor 26 of the cores 20 not set by the circuits 40.

Upon the application of the (p half-amplitude current pulse to the write conductors 26' of the columns 'b and c by the operationof the switch 10 coincidentally with the application of a (p half-amplitude current pulse to the write conductor '33 of the row 2 by the operation of the access switch 50, the cores 31 intersected by the conductors 26 of columns b and c and conductor 33 of row 2 will be set in accordance with the principles of coincident. current core switching generally. In this manner the originally read out binary information word 011 0" is restored to the row 2 of the matrix. It should be noted:

I that, according to a feature of this invention, the output from the switch 10 to the loads, herein the columns of cores of the matrix 30, can. be controlled with precision. since this currentis equal to the activating'current applied by thesource 60.

When the half-amplitude current pulse is applied tetheactivating windings 22 of thecores 20, all of the cores 20 set by the' operation of the circuits- 40 will be reset. All of'the cores20 of the switch 10 will now'be in a condition to be again set in accordance'withan information;

5. word read from another row or with a new information word to be stored in that row.

It is to be understood that although a magnetic core storage matrix is shown in connection with the present nvention, other loads requiring well regulated current mputsselectively applied may be driven by the present switch 10. In addition, switching circuits other than those advantageously employed herein may be used to perform the switching and logic functions of amagnetic memory arrangement in which the switch of the present inventlon is also employed. It is further to be understood that what has been described is only one illustrative embodiment of the principles of the present invention and modification and changes may be made therein by one skilled in th e art without departing from the spirit and scope of this invention.

What is claimed is:

1 An electrical circuit comprising a plurality of magnetic cores each having a substantially rectangular hysteresis characteristic, output and activating windings for each of said cores, a first circuit means for' connecting the activating winding ofeach of said cores to the activating winding of a succeeding core, load means associated with each of said cores, a second circuit means for serially connecting the activating winding of each of said cores respectively through the output winding of the same core and one of said loa'd means to the activating winding of a succeeding core, means for selectively setting particular ones of said cores, and means including a current source for applying a switching current pulse to said activating windings.

2. An electrical circuit as claimed in claim 1, in which each of said output windings and said activating windings has a unilateral conducting element connected to the output side thereof.

3. An electrical circuit comprising a series of magnetic cores each having a substantially rectangular hysteresis characteristic, input, output, and activating windings for each of said cores, the output side of each of said activating windings being connected respectively to the input side of each of said output windings, a first plurality of circuit means for connecting respectively said output side of each of said activating windings to the input side of a succeeding activating winding, a plurality of load means, a second plurality of circuit means including respectively said plurality of load means for connecting respectively said output side of each of said activating windings through the output winding of the same core to the input side of a succeeding activating winding, a third plurality of circuit means individually connected to said input windings and including a first current source, means for controlling said third plurality of circuit means to selectively set particular cores of said plurality of cores, and means including a second current source for applying a switching current pulse to the activating winding of the first core of said series, said first and second plurality of circuit means each being isolated in a manner suchas to comprise only two alternate paths for said switching current pulse at said output side of each of said activating windings.

4. An electrical circuit as claimed in claim 3 in which each circuit means of said first and said second plurality of circuit means has included therein a unilateral conducting element.

5. An electrical circuit comprising a plurality of magnetic cores each having a substantially rectangular hysteresis characteristic, means for setting predetermined cores of said plurality of cores, output and activating windings for each of said cores, a source of activating current, a first current path for said activating current including said activating windings in series, load means for each of said cores, and a second current path for said activating current including each of said activating windings and the output windings and load means of said predetermined cores in series.

6. In an information storage system, first groups of magnetic cores, a second group of magnetic cores individually associated with each of said first groups of cores, each of said cores having a substantially rectangular hys-. teresis characteristic, a plurality of switching leads, each of said switching leads being inductively coupled to the cores of each of said first groups of cores respectively and each of said switching leads being associated respectively with each of the cores of said second group, means for setting particular cores in said second group in accordance with a predetermined code, an activating and an output winding for each core of said second group of cores, circuit means including a current source for applying an activating current to said activating windings, said circuit means including a first current path for said activating current including said activating windings in series and a second current path for said activating current including each of said activating windings and the output windings and switching leads of said particular cores in' said second group in series.

7. A selecting switch comprising a plurality of magnetic cores each being capable of assuming two conditions of magnetic remanence, input, output, and activating windings for each of said cores, means including a first current source for selectively applying setting currents to said input windings to set particular cores of said plurality of cores in accordance with a predetermined code, load means for each of said cores, first circuit means for connecting said activating windings, said output windings, and said load means of each of said cores in series, and a plurality of second circuit means for shunting respectively the output windings and load means of each of said cores.

8. A selecting switch as claimed in claim 7, in which each of said second circuit means includes a unidirectional current element and also comprises means including a current source for applying an activating current to said activating windings to switch said particular cores, the output windings of said particular cores being in a sense such that the voltage induced thereacross by said core switching causes said activating current to pass through the first circuit means of said particular cores.

9. A selecting switch as claimed in claim 8, each of said load means comprising a switching conductor inductively coupled to a plurality of information storage elements each capable of assuming two stable states responsive to applied activating currents.

10. A selecting switch comprising a plurality of magnetic cores each having a substantially rectangular. hysteresis characteristic, an output and an activating winding for each of said cores, load means individually associated with each of said cores, a plurality of circuit means for connecting respectively the output side of the activating winding of each of said cores to the input side of the activating winding of another of said cores, each of said circuit means comprising a pair of parallel paths, one of said paths including the output winding of the core having the activating winding from which said circuit means is connected, a unilateral conducting element, and a load means, the other of said paths including a unilateral conducting element, means for selectively setting particular ones of said cores in accordance with a predetermined code, and means including a current source for applying activating current to said activating windings to switch said particular ones of said cores, said output windings on said particular ones of said cores being in a sense such that the switching of said cores induces a voltage thereacross in a direction to control the conduction of said activating current through a selected one of said paths of said circuit means connected to the activating windings of said particular ones of said cores.

11. An electrical circuit comprising a plurality of mag netic cores each having a substantially rectangular hysteresis characteristic, an input, an output, and an activating winding for each of said cores, a load means associated with 'eachofsaid cores, a plurality of'eireuit means forc'onnecting'the output side oftheactivating winding of each'core of-said plurality of cores'to' the-input side of the activating winding of a respective succeeding core of said plurality of cores, each of said plurality of circuit means comprising a first and a second conducting path,

said first path including a first unilateral conducting means connected to the activating winding of a core and said second path including the output winding of said lastmentioned core, a second unilateral conducting element, and one of said load means connected to said last mentioned output winding; meansfor' selectively apply ing setting currents to said input' windings toiset particular ones of said cores in one condition of reman'ent mag netization, and means 'forapplying an activating current to said activating windings to switch said particular ones of said cores to the other condition of remanent mag n'etization, said output windings of said particular cores being in a sense suchthat the voltage induced thereacross by said core switching causes said activating current to pass through the portions of said Secondpath of said circuit means connected to' the activating windings of said particular cores. 7

12. In an information memory matrix, a first and a second plurality of magnetic cores each being. capable of assuming two conditions of magnetic remanence, said first plurality of cores beingarranged in rows'and columns, the coresof each of said columns having 'a switching lead threaded therethrough, an activating, an input, and an output winding for each core of said second plu-' 'rality of cores, means for selectively applying current pulses to i said input windin 16 {set particularones of said second plurality of cores to' dn'e'ofsaidfconditions of magnetic remanence; a plurality fcirc uit means for connecting respectively the 'qutpm's'ideof the activating Winding of first cores-of said second pluralityof cores to the input side of theactivating' winding of a succeeding'second core of said second plurality of cores, each of said pluralityof circuit means including two paths, one of said paths including the o ut'put "winding of a said first core of said second plurality of cores'and a switching lead, means for applying an activating current pulse to said activating windings to-switcn said particular ones of said secondvplurality of cores to the other condition of magnetic remanence, said output windings of said" particular cores being in a sense'such thatt'he voltage induced thereacross by said core switching-causes said activating current to pass throughthe said ones of said paths of said circuit means connected to the activating windings of said particular cores, which said ones of said paths include switching leads. I

I 13. In an information storage system according to claim 12, each of said activating windings and said output windings having a unidirectional current element connected in the output side thereof. p 7

References Cited in the file of this patent UNITED STATES PATENTS 2,792,564 Ramey et al. May 14, 1957 

